body {
    background: rgba(255, 255, 255, 0);
    margin: 0;
    padding: 0;
    height: 100%;
    display: flex;
    align-items: center;
    justify-content: center;
}
.app {
    border-radius: 10px;
    display: flex;
    justify-content: center;
    align-items: center;
    width: 100%;
    height: 100vh;
    font-weight: bold;
    color: white;
    font-size: 36px;
    text-align: center;
    -webkit-app-region: drag; /* 使内容可拖拽 */
}
.app-normal {
    background: rgba(31, 127, 229, .6);
}
.app-warning {
    background: rgba(252, 2, 47, .6);
}
.app-body {
    -webkit-app-region: no-drag;
}
.app-countdown-btn {
    margin-left: 28px;
}
.app-countdown-btn>i {
    cursor: pointer;
}